The field of the present invention relates to optical data readers such as barcode readers. More particularly, the field of the present invention relates to the controlling of optical data readers in response to certain external conditions.
Many conventional optical data readers incorporate circuitry to switch the reader into an inactive or “sleep” mode when the reader is not used for a predetermined time (e.g., one minute). The sleep mode is typically used to reduce power consumption, save energy, and reduce wear and tear on moving components. In flying spot laser barcode scanners, the laser is typically turned off when the scanner is in the sleep mode. Turning the laser off also promotes laser safety by minimizing the chances that the eyes of an operator or a bystander will be exposed to an excessive amount of laser light.
Systems that incorporate a sleep mode require a mechanism to return a sleeping system to the operational mode, i.e., to “wake up” the system. One conventional prior art approach for implementing a wake-up function in a barcode scanner is to use a passive photodetector, aimed into the scanning volume of the scanner, to monitor changes in ambient light, (arriving, e.g., from a ceiling light fixture). When an object is moved into the scanning volume, the shadow of the object will usually fall on the photodetector, thereby changing the amount of ambient light reaching the photodetector. The photodetector output will change in response to the changes in detected light. When a change is detected (e.g., from low light to high light or vice versa), the system switches from sleep mode into the operational mode.
It can, however, be difficult to implement an ambient light detecting system that will reliably wake a data reader up from the sleep state every time an object is passed in the vicinity of the data reader. This is due in part to the wide variety of environments in which the data readers are used, ranging from dimly lit to brightly lit environments.
Because of the difficulty of implementing a wake-up function based solely on detected variations of ambient light, some prior art systems incorporate a manually operated pushbutton wake-up switch. The pushbutton switch is used by the operator to wake up the system whenever the automatic wakeup system fails to operate properly. In some of these prior art systems, the pushbutton switch is also used to control the volume of the read-acknowledgement beeps that are generated after a barcode is successfully read.
Unfortunately, a significant number of additional assembly steps are needed to implement a backup wake-up function using a mechanical pushbutton switch. These include, for example, punching a hole in the data reader chassis, mounting the switch into the hole, providing a wiring harness to connect with the switch, and making the connection between the switch and the harness. When the data reader is used in environments where contamination is possible (e.g., in a supermarket checkout scanner, where spills may occasionally occur), special care must be taken to protect the switch from contamination. These steps may further increase the component cost and the cost of assembly. Due in part to these disadvantages, the inventors have recognized a need for a reliable wake-up system and/or function control system that does not rely on an independently mounted mechanical switch.
Safety is another important consideration in optical data readers. In particular, with laser-based barcode scanners, it is desirable to minimize exposure to laser light.
One specific situation where undesired exposure to laser light can occur is when the window in a console-mounted barcode scanner is removed for servicing (e.g., to replace a scratched window). A current approach for minimizing this risk involves providing two windows: an inner window and an outer window. With this double window configuration, the outer window can be replaced without exposing the laser source, because the inner window remains in its position while the outer window is being replaced. The double window configuration, however, increases the component count, the weight, and the cost of the resulting system, and complicates the manufacturing process. Due in part to these disadvantages; the inventors have recognized a need to reduce the risk of laser light exposure without relying on a double window configuration.